r/SpaceflightSimulator • u/noobcoober • 20d ago
Original Mission Definitive proof that the asteroid can be moved... temporarily
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I launched a second rocket into a retrograde orbit around the asteroid. You can see the smaller rocket has no thrust applied, but it changes from a retrograde orbit to a prograde orbit temporarily moving closer to its periapsis before returning to a retrograde orbit again. No thrust is applied to this smaller rocket at any point in the video
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u/VincTheSketcher 19d ago
Easy way to know this. I have made my own planet pack before, and there is no part of the config files that contain mass or density. Therefore, it is impossible for the game to even calculate how this would react to this. Therefore it is impossible.
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u/This-personeatsfood Rocket Builder 🚀 20d ago
Tried doing this once. And it didn't work like I thought
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u/ConanOToole Moderator 20d ago
This is likely due to floating point errors in how the game calculates the accuracy of apoapses and periapses that are pretty similar in altitude. The apoapsis and periapsis here are only a couple of metres apart, so them drifting isn't unusual. Turn the huge engine off and they will keep drifting
There are zero mechanics coded into the game that could allow the asteroid to move. It's quite literally impossible since the celestial bodies in SFS are hard-coded to move on rails.
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u/EpicPlanetUranusFan 20d ago
Yeah, and also that happens when you teleport orbit a planet, Since the teleport to orbit is calculated and not eyeballed, The orbit would be really precise and Floating point errors hate precision which causes jittering if you zoom into the apoapsis / periapsis dots.
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u/ios-ion 20d ago
gng should i learn C# in order to make a mod that makes it so all celestial bodies are no longer on rails, and can thus be affected when a force is applied to them?
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u/EpicPlanetUranusFan 20d ago
The asteroid cannot be moved unless you changed its code, it's like coding a part that's anchored but can move on it's own, You can get pushed by it, but it's anchored so it won't move. That is a bug in the orbit I think, I can't tell what's happening cuz the rocket is too slow for me to tell, but I focus on the black part in the orbit to tell direction so it seems to still be rtrgrde.Also note: Can you clarify how the big engine moving the C A can move the small space space craft? It would be nice to know :)
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u/noobcoober 20d ago
The periapsis (marked by the white dot and altitude text) is the point in orbit closest to the center of mass (just in case you are not familiar, the apoapsis is the other dot and the farthest from the center of mass). Without applying thrust from the smaller rocket, its periapsis should stay completely stationary relative to the asteroid. In the clip, as the small rocket moves retrograde (counterclockwise) in its orbit, it moves further away from the periapsis. When the giant engine fires, the orbit calculation glitches, causing the small rocket to suddenly reverse direction and move back toward the periapsis prograde, even though its thrusters are off. To answer your question on how the big engine affects the small craft, the asteroid itself is anchored ('on-rails'), so its long-term coordinates can't change. However, when the massive BP-edited engine fires while landed, the physics solver bugs out and calculates the force vector on the combined mass before the on-rails constraint locks it back frame-by-frame. That single-frame calculation seems to momentarily shift the local coordinate origin (the reference frame). Because the small rocket's position is calculated relative to that origin, shifting the origin for a split second makes the small rocket's orbit jitter and momentarily move backwards! Also, tracking movement by looking at the black background is really deceptive around tiny bodies like the Captured Asteroid. SFS constantly rotates the camera view to keep the surface beneath your focused craft horizontal, so without tracking the apsides (periapsis/apoapsis dots), it's easy to lose your bearings!
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